dtrace probes in kexts

13 Jul 2017

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Hello list,

So we thought we would finally support the Solaris style in-source dtrace
probes, which work quite differently in Apple.

Following the section "BUILDING CODE CONTAINING USDT PROBES" in manpage for
dtrace;

Going through the steps of "dtrace -h -s dtrace.d" to produce the Apple
header "dtrace.h", to include when compiling kext, we eventually end up with:

/tmp/zfs.kext failed to load - (libkern/kext) link error; check the
system/kernel logs for errors or try kextutil(8).

# kextutil /tmp/spl.kext/ /tmp/zfs.kext/
(kernel) kxld[net.lundman.zfs]: The Mach-O file is malformed: Invalid
section type: 15.

Which seems to come directly from the dtrace produced code:

#define ZFS_TYPEDEFS "___dtrace_typedefs$zfs$v2"
#define ZFS_STABILITY
"___dtrace_stability$zfs$v1$1_1_0_1_1_0_1_1_0_1_1_0_1_1_0"

        __asm__ volatile(".reference " ZFS_TYPEDEFS);             \
        __dtrace_probe$zfs$zfs__dbgmsg$v1$63686172202a(arg0); \
        __asm__ volatile(".reference " ZFS_STABILITY); \

Produced from libkern/kxld/kxld_sect.c:

    case S_DTRACE_DOF:
    default:
        rval = KERN_FAILURE;
        kxld_log(kKxldLogLinking, kKxldLogErr, kKxldLogMalformedMachO
            "Invalid section type: %u.", sect->flags & SECTION_TYPE);
        goto finish;

Am I missing a step, or does in-source dtrace probes no longer work in KEXTs?

Lund

--
Jorgen Lundman       | <lundman@lundman.net>
Unix Administrator   | +81 (0)90-5578-8500
Shibuya-ku, Tokyo    | Japan

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